This is old ground, the detractors say. I'm not 100% sure about that.
On my thesis experiment, one of the researchers told us that one of his wife's college friends had a student job that among other duties involved cleaning up some of the labs where this kind of research went on. I gathered that he thought this was the cloth-vs-wire surrogate mother experiment, but I don't think the dates work for that--he was only about 10 years older than me. At any rate, the cleaning lady was softhearted, and would take baby monkeys out of their cages and cuddle them--and apparently never got caught at it.
Hmm. If the monkey was disturbed and would run or bite, I'd bet she wouldn't cuddle it much, but if it wasn't so bad off, I'd bet the contact would make it happier. I think I see a way results could be skewed with nobody having a clue.